System for regulating focus current and voltage in a television camera



Nov. 28, 1967 w. J. COSGROVE 3,

SYSTEM FOR REGULATING FOCUS CURRENT AND VOLTAGE IN A TELEVISION CAMERA Filed March 19, 1965 4MPL/F/EK 1 AMPL lF/EK 1 h l I Q 1 I l I "I l 3 l. J

' INVENTOR. W/u/AM J Case/(ova zaomel United States Patent 3,355,621 SYSTEM FOR REGULATING FOCUS CURRENT AND VOLTAGE IN A TELEVISION CAMERA William J. Cosgrove, Linwood, Pa, assignor to Radio Corporation of America, a corporation of Delaware Filed Mar. 19, 1965, Ser. No. 441,186 7 Claims. (Cl. 315-31) This invention relates to current and voltage regulating apparatus and particularly to apparatus of this character which is capable not only of maintaining substantially stable current and voltage sources but also of insuring that any change in current is accompanied by a corresponding change in voltage.

It often is desirable to maintain the current in one circuit and the voltage in another circuit substantially constant and in a fixed relation to one another. For example, in the operation of television camera apparatus embodying a pickup tube of the image orthicon type, the scanning beam focus is effected under the joint control of an electrostatic field produced from within the tube and of an electromagnetic field produced from outside of the tube. The electrostatic field producing means is energized by voltage and the electromagnetic field producing means is energized by current. Because of the environment of such a pickup tube and some of its energizing apparatus in the normally enclosed space of a television camera, one or both of the beam focussing systems is subjected to heat generated within the camera. Any change in the temperature of such apparatus tends to change either or both of the current and voltage supplied to the focussing systems. It is desirable that both focussing current and voltage be maintained as constant as possible but it is also equally desirable that any changes in the current, for example, be accompanied by corresponding changes of the voltage.

It, therefore, is an object of the present invention to provide a current and voltage regulating system in which the current and voltage are maintained substantially constant and any current changes are reflected in corresponding changes of the voltage.

In accordance with this invention a voltage representative of the current to be regulated is compared with and made substantially identical to a stable reference voltage. A sample of the voltage to be regulated then is compared with and made substantially identical to the current representative voltage.

For a better understanding of the invention, reference now is made to the following description which is taken in conjunction with the single figure of the accompanying drawing.

The pickup tube 1 is illustrated as being of the well known image orthicon type which includes such electrodes as an electron gun and multiplier apparatus 2, an electrostatic beam focussing electrode 3 internally of the tube. Externally, the pickup tube is provided with auxiliary apparatus such as an electromagnetic focussing coil 4 and a beam deflection coil 5.

The electrostatic focussing electrode 3, forming part of an electron-optical beam focussing lens, is provided with a suitable operating potential derived from a potentiometer 6 which forms part of a voltage divider 7 also including resistors 8 and 9 connected in the emitter electrode circuit of a voltage regulating transistor 11, the collector electrode of which is connected to a voltage source E Operating current is provided for the focussing coil 4 from the source E by a circuit connected to the collector electrode of a current regulating transistor 12 in the emitter electrode circuit of which is connected a voltage divider 13 comprising resistors 14 and 15.

The current regulating transistor 12 preferably is of the type having a large transmission ratio of collector current to base current. The emitter current, therefore, is

substantially equal to the collector current so that the voltage drop across the voltage divider 13 is essentially representative of the current flowing in the collector electrode circuit which includes the focussing coil 4. A sample of the voltage drop across the voltage divider 13 is taken at the junction point 16 between the resistors 14 and 15. This voltage sample is representative of the current in the coil 4.

The voltage sample taken at the point 16 of the voltage divider 13 is compared with a stable reference voltage relative to ground present at the ungrounded terminal of a zener diode 17. This comparison is made by a differential amplifier 18 comprising transistors 19 and 21. The stable reference voltage is applied to the base of transistor 19 and the sample voltage is applied to the base of transistor 21. The collector and emitter electrode circuits of these transistors are identical so that any difference between the respective voltages applied to the base electrodes of these transistors is effective to produce an error signal at an output terminal 22 connected to the collector electrode of transistor 21. This error signal is applied through an amplifier 23 to the base electrode of the current regulating transistor 12 and is effective to suitably alter the collector-to-emitter electrode current flow in this transistor so as to produce a sample voltage at the point 16 of the voltage divider 13 which is substantially equal to the reference voltage across the zener diode 17. In this way, the current in the focussing coil 4 is regulated and the voltage drop across the voltage divider 13 is substantially stabilized.

The voltage at the point 24 of the voltage divider 7 is representative of the voltage applied to the focus electrode 3 of the pickup tube 1. This sample voltage is compared with the voltage drop across the voltage divider 13 by a second differential amplifier 25 which is similar in character to the differential amplifier 18. In this case, the essentially stable reference voltage applied to the base of transistor 26 is representative of the current in the focus coil 4 and is used as a comparison reference for the sample voltage at the point 24 of the voltage divider 7 which is applied to the base of transistor 27. Any difference in these two voltages produces an error signal at an output terminal 28 connected to the collector electrode of the transistor 27. This error voltage is then applied through an amplifier 29 to the base electrode of the voltage regulating transistor 11. The collector-to-emitter current flow in this transistor, thus, is altered suitably to produce a voltage derived from the potentiometer 6 and applied to the electrostatic focus electrode 3 which maintains a predetermined relationship with the current through the electromagnetic focus coil 4. It has been found that substantially perfect tracking between the electrostatic focus voltage and the electromagnetic focus current can be obtained by suitably proportioning the values of resistors 8 and 9 and by the adjustment of potentiometer 6 of the voltage divider 7.

What is claimed is:

1. A system for regulating current in one circuit and voltage in a related circuit, comprising:

means including a current regulating device for supplying current to said one circuit;

means coupled to said current regulating device to produce a first sample voltage representative of the current supplied to said one circuit;

means responsive to said first sample voltage and to a fixed reference voltage to produce a first error signal representative of any difference between said first sample and said reference voltages;

means responsive to said first error signal to so control said current regulating device as to maintain the current in said one circuit and said first sample voltage substantially constant;

means including a voltage regulating device for supplying voltage to said related circuit; means coupled to said voltage regulating device to produce a second sample voltage representative of the voltage supplied to said related circuit; means responsive to said second sample voltage and to a voltage representative of the current supplied to said one circuit to produce a second error signal representative of any difference between said second sample and said current representative voltages; and means responsive to said second error signal to so control said voltage regulating device as to maintain the voltage in said related circuit substantially constant and in fixed relation to the current in said one circuit. 2. In a television camera including an image pickup tube having a current energized electromagnetic focus coil and a voltage energized electrostatic focus electrode, a system for regulating focus current and voltage, comprising:

a current regulating transistor having a current control electrode; means including said current regulating transistor for supplying energizing current to said focus coil; means connected to said current regulating transistor to produce a current indicating voltage representative of current fiow in said focus coil;

a source of stable reference voltage;

a first comparator responsive to a first sample of said current indicating voltage and to said reference voltage to produce a first error signal representative of any difference between said first sample and said reference voltage;

means for impressing said first error signal upon the control electrode of said current regulating transistor, thereby to so control conductivity of said current regulating transistor as to maintain the current in said focus coil and the voltage of said current indicating means substantially constant;

a voltage regultaing transistor having a current con trol electrode;

means including said voltage regulating transistor for developing and supplying an energizing voltage to said focus electrode;

a second comparator responsive to a second sample taken from said voltage developing means and to said current indicating voltage to produce a second error signal representative of any difference between said second sample and said current indicating voltage; and

means for impressing said second error signal upon the control electrode of said voltage regulating transistor, thereby to so control conductivity of said voltage regulating transistor as to maintain said focus electrode voltage substantially constant and in fixed relation to said focus coil current.

3. In a television camera including an image pickup tube having a current energized electromagnetic focus coil and a voltage energized electrostatic focus electrode. a system for regulating focus current and voltage, comprising:

a current regulating transistor having base. emitter and collector electrodes;

means including the collector-to-emitter electrode circuit of said current regulating transistor for supplying energizing current to said focus coil;

means connected in the collector-to-emitter electrode circuit of said current regulating transistor to produce a current indicating voltage representative of current flow in said focus coil;

a source of stable reference voltage;

a first comparator responsive to a first sample of said current indicating voltage and to said reference voltage to produce a first error signal representative of any difference between said first sample and said reference voltage;

means for impressing said first error signal upon the base electrode of said current regulating transistor, thereby to so control conductivity of said current regulating transistor as to maintain the current in said focus coil and the voltage of said current indicating means substantially constant;

a voltage regulating transistor having base, emitter and collector electrodes;

means including voltage developing apparatus connected in the collector-to-emitter circuit of said voltage regulating trunsisior emitter electrode for supplying an energizing voltage to said focus electrode;

a second comparator responsive to a second sample taken from said energizing voltage supplying means and to said current indicating voltage to produce a second error signal representative of any difference between said second sample and said current indicating voltage; and

means for impressing said second error signal upon the base electrode of said voltage regultaing transistor, thereby to so control conductivity of said voltage regulating transistor as to maintain said focus electrode voltage substantially constant and in fixed relation to said focus coil current.

4. In a television camera including an image pickup tube having a current energized electromagnetic focus coil and a voltage energized electrostatic focus electrode, a system for regulating focus current and voltage, comprising:

a current regulating transistor having base, emitter and collector electrodes;

means connecting said current regulating transistor collector electrode through said focus coil to a source of current;

means connected to said current regulating transistor emitter electrode to produce a current indicating voltage representative of current flow in said focus coil;

a source of stable reference voltage;

a first comparator responsive to a first sample of said current indicating voltage and to said reference voltage to produce a first error signal representative of any difference between said first sample and said reference voltage;

means for impressing said first error signal upon the base electrode of said current regulating transistor, thereby to so control conductivity of said current regulating transistor as to maintain the current in said focus coil and the voltage of said current indicating means substantially constant;

a voltage regulating transistor having base, emitter and collector electrodes;

means connecting said voltage regulating transistor to a source of voltage;

voltage developing means connected to said voltage regulating transistor emitter electrode;

means connecting said voltage developing means to said focus electrode;

a second comparator responsive to a second sample taken from said voltage developing means and to said current indicating voltage to produce a second error signal representative of any difference between said second sample and said current indicating voltage; and

means for impressing said second error signal upon the base electrode of said voltage regulating transistor, thereby to so control conductivity of said voltage regulating transistor as to maintain said focus electrode voltage substantially constant and in fixed relation to said focus coil current.

5. In a television camera including an image pickup tube having a current energized electromagnetic focus coil and a voltage energized electrostatic focus electrode, a system for regulating focus current and voltage, comprising:

a current regulating transistor having base, emitter and collector electrodes;

means connecting said current regulating transistor collector electrode through said focus coil to a source of current;

a first voltage divider connected to said current regulating transistor emitter electrode;

a source of stable reference voltage;

a first comparator comprising a first pair of voltage comparison transistors, each having base, emitter and collector electrodes;

means similarly energizing the collector and emitter electrodes of said first pair of voltage comparison transistors;

means coupling the base electrodes of said first pair of voltage comparison transistors respectively to said reference voltage source and to said first voltage divider to produce a first error signal at the collector electrode of that transistor whose base electrode is coupled to said first voltage divider;

means for impressing said first error voltage upon the base electrode of said current regulating transistor, thereby to so control conductivity of said current regulating transistor as to maintain the current in said focus coil and the voltage across said first voltage divider substantially constant;

a voltage regulating transistor having base, emitter and collector electrodes;

means connecting said voltage regulating transistor to a source of voltage;

a second voltage divider connected to said voltage regulating transistor emitter electrode;

means connecting said second voltage divider to said focus electrode;

a second comparator comprising a second pair of voltage comparison transistors, each having base, emitter and collector electrodes;

means similarly energizing the collector and emitter electrodes of said second pair of voltage comparison transistors;

means coupling the base electrodes of said second pair of voltage comparison transistors respectively to said first and second voltage dividers to produce a second error signal at the collector electrode of that transistorwhose base electrode is coupled to said second voltage divider; and

means for impressing said second error voltage upon the base electrode of said voltage regulating transistor, thereby to so control conductivity of said voltage regulating transistor as to maintain said focus electrode voltage substantially constant and in fixed relation to said focus coil current.

6. In a television camera including an image pickup tube having a current energized electromagnetic focus coil and a voltage energized electrostatic focus electrode, a system for regulating focus current and voltage, comprising:

a current regulating transistor having base, emitter and collector electrodes;

means connecting said current regulating transistor collector electrode through said focus coil to a source of current;

a first voltage divider connected to said current regulating transistor emitter electrode;

a source of stable reference voltage;

a first comparator comprising a first pair of voltage comparison transistors, each having base, emitter and collector electrodes;

means similarly connecting the collector and emitter electrodes of said first pair of voltage comparison transistors to an energy source;

means coupling the base electrodes of said first pair of voltage comparison transistors respectively to said reference voltage source and to said first voltage divider to produce a first error signal at the collector electrode of that transistor whose base electrode is coupled to said first voltage divider;

means for impressing said first error voltage upon the base electrode of said current regulating transistor, thereby to so control conductivity of said current regulating transistor as to maintain the current in said focus coil and the voltage across said first voltage divider substantially constant;

a voltage regulating transistor having base, emitter and collector electrodes;

means connecting said voltage regulating transistor to a source of voltage;

a second voltage divider connected to said voltage regulating transistor emitter electrode;

means connecting said second voltage divider to said focus electrode;

a second comparator comprising a second pair of voltage comparison transistors, each having base, emitter and collector electrodes;

means similarly connecting the collector and emitter electrodes of said second pair of voltage comparison transistors to an energy source;

means coupling the base electrodes of said second pair of voltage comparison transistors respectively to said first and second voltage dividers to produce a second error signal at the collector electrode of that transistor whose base electrode is coupled to said second voltage divider; and

means for impressing said second error voltage upon the base electrode of said voltage regulating transistor, thereby to so control conductivity of said voltage regulating transistor as to maintain said focus electrode voltage substantially constant and in fixed relation to said focus coil current.

7. In a television camera including an image pickup tube having a current energized electromagnetic focus coil and a voltage energized electrostatic focus electrode, a system for regulating focus current and voltage, comprising:

a current regulating transistor having base, emitter and collector electrodes;

means connecting said current regulating transistor collector electrode through said focus coil to a source of current;

a first voltage divider connected to said current regulating transistor emitter electrode;

a source of stable reference voltage;

a first differential amplifier comprising a first pair of voltage comparison transistors, each having base, emitter and collector electrodes;

means similarly connecting the collector and emitter electrodes of said first pair of voltage comparison transistors to an energy source;

means coupling the base electrodes of said first pair of voltage comparison transistors respectively to said reference voltage source and to said first voltage divider to produce a first error signal at the collector electrode of that transistor whose base electrode is coupled to said first voltage divider;

means including a first amplifier for impressing said first error voltage upon the base electrode of said current regulating transistor, thereby to so control conductivity of said current regulating transistor as to maintain the current in said focus coil and the voltage across said first voltage divider substantially constant;

a voltage regulating transistor having base, emitter and collector electrodes;

means connecting said voltage regulating transistor to a source of voltage;

a second voltage divider connected to said voltage regulating transistor emitter electrode;

means connecting said second voltage divider to said focus electrode;

a second differential amplifier comprising a second pair of voltage comparison transistors, each having base, emitter and collector electrodes;

means similarly connecting the collector and emitter electrodes of said second pair of voltage comparison transistors to an energy source;

means coupling the base electrodes of said second pair of voltage comparison transistors respectively to said first and second voltage dividers to produce a second error signal at the collector electrode of that transistor whose base electrode is coupled to said second voltage divider; and

means including a second amplifier for impressing said second error voltage upon the base electrode of said voltage regulating transistor, thereby to so control References Cited UNITED STATES PATENTS Fathauer 315-31 Fathauer et a1. 3l531 Shapiro 317-149 Dupire et al. 307-885 JOHN W. CALDWELL, Primary Examiner.

R. A. BLUM, Assistant Examiner. 

1. A SYSTEM FOR REGULATING CURRENT IN ONE CIRCUIT AND VOLTAGE IN A RELATED CIRCUIT, COMPRISING: MEANS INCLUDING A CURRENT REGULATING DEVICE FOR SUPPLYING CURRENT TO SAID ONE CIRCUIT; MEANS COUPLED TO SAID CURRENT REGULATING DEVICE TO PRODUCE A FIRST SAMPLE VOLTAGE REPRESENTATIVE OF THE CURRENT SUPPLIED TO SAID ONE CIRCUIT; MEANS REPSONSIVE TO SAID FIRST SAMPLE VOLTAGE AND TO A FIXED REFERENCE VOLTAGE TO PRODUCE A FIRST ERROR SIGNAL REPRESENTATIVE OF ANY DIFFERENCE BETWEEN SAID FIRST SAMPLE AND SAID REFERENCE VOLTAGES; MEANS RESPONSIVE TO SAID FIRST ERROR SIGNAL TO SO CONTROL SAID CURRENT REGULATING DEVICE AS TO MAINTAIN THE CURRENT IN SAID ONE CIRCUIT AND SAID FIRST SAMPLE VOLTAGE SUBSTANTIALLY CONSTANT; MEANS INCLUDING A VOLTAGE REGULATING DEVICE FOR SUPPLYING VOLTAGE TO SAID RELATED CIRCUIT; MEANS COUPLED TO SAID VOLTAGE REGULATING DEVICE TO PRODUCE A SECOND SAMPLE VOLTAGE REPRESENTATIVE OF THE VOLTAGE SUPPLIED TO SAID RELATED CIRCUIT; MEANS RESPONSIVE TO SAID SECOND SAMPLE VOLTAGE AND TO A VOLTAGE REPRESENTATIVE OF THE CURRENT SUPPLIED TO SAID ONE CIRCUIT TO PRODUCE A SECOND ERROR SIGNAL REPRESENTATIVE OF ANY DIFFERENCE BETWEEN SAID SECOND SAMPLE AND SAID CURRENT REPRESENTATIVE VOLTAGES; AND MEANS RESPONSIVE TO SAID SECOND ERROR SIGNAL TO SO CONTROL SAID VOLTAGE REGULATING DEVICE AS TO MAINTAIN THE VOLTAGE IN SAID RELATED CIRCUIT SUBSTANTIALLY CONSTANT AND IN FIXED RELATION TO THE CURRENT IN SAID ONE CIRCUIT. 